Re: [visad] GOES AREA goerefencing

• To: Luis Martín Pomares <luis.martin@xxxxxxxxxxx>
• Subject: Re: [visad] GOES AREA goerefencing
• From: Tom Whittaker <whittaker@xxxxxxxx>
• Date: Mon, 28 Mar 2011 13:42:59 -0500

If you were required to adjust the subscripts for getting the starting
line and element (dir[5] and dir[6] in your original code, but you
changed to dir[6] and dir[7]), then I would suggest that you would
have to change the subscript values in the "setRes()" call as well.
These indicies are elements of the AREA File "directory block"
(described here:
<http://www.ssec.wisc.edu/mcidas/doc/prog_man/2006/formats-1.html#13797>

The original code may have been based on an AREA file that was created
without the initial "word" (position within the dataset) and hence,
all of the index values would be off by 1...

Hope that helps.

tom

2011/3/25 Luis Martín Pomares <luis.martin@xxxxxxxxxxx>:
> Dear all,
>
> I am trying to georeference GOES AREA files using visad. I am doing this in
> MATLAB. However, I obtain strange value. I want to give the latitude and
> longitude and obtain a row and column value to access the matrix of
> radiances from [1,1].
>
> In the example of visad it says I have to do the following:
>
> af = new AreaFile("/home/user/mcidas/data/AREA0001");
> dir=af.getDir();
> nav=af.getNav();
> GVARnav ng = new GVARnav(nav);  // XXXXnav is the specific implementation
>  ng.setImageStart(dir[5], dir[6]);
>  ng.setRes(dir[11], dir[12]);
>  ng.setStart(1,1);
>
> However w5 is a date, so I change the w5 by w6 and w7:
>
> W6
> image line coordinate of area line 0, element 0
> W7
> image element coordinate of area line 0,
> element 0
>
> I have tried to see the correspondence the point that I get for the sub
> satellite but it is not ok. What I am doing is this:
>
> clc;clear all;close all;
> import edu.wisc.ssec.mcidas.*
> file='D:\Irsolav\GOES\GOES_DATA\goes08.2000.303.144514.BAND_01';
> data=AreaFile(file);
>
> dir=data.getDir();
> nav=data.getNav();
>
> ng=GVARnav(nav); %XXXXnav is the specific implementation
> ng.setImageStart(dir(6),dir(7));
> ng.setRes(dir(11), dir(12)); %
> ng.setStart(1,1);
> ng.setMag(1,1);
> %......................
> disp('LINELE'); %subsatellite point for GOES 8
> latlon=[0;-75]
> linele_area=ng.toLinEle(latlon)
>
> disp('LATLON TRANSFORMATION');
> % linele=[1;1]
> latlon=ng.toLatLon(linele_area)
> %ng.toLatLon(double[][] linele);   %public abstract double[][]
> toLatLon(double[][] linele)
>
> disp('IMAGE COORDINATE TRANSFORMATION');
> linele_image=ng.areaCoordToImageCoord(linele_area)
>
> disp('Transformation from IMAGE coordinates to AREA coordinates');
> linele_area=ng.imageCoordToAreaCoord(linele_image)
>
> % disp('Transformation from IMAGE coordinates to AREA coordinates - version
> 2');
> % linele_area=ng.imageCoordToAreaCoord(linele_image)
>
> latlon=ng.toLatLon(linele_area)
> %By convention, latitudes are positive North (negative South), and
> longitudes are positive East (negative West).
>
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>



-- 
Tom Whittaker
University of Wisconsin-Madison
Space Science & Engineering Center (SSEC)
Cooperative Institute for Meteorological Satellite Studies (CIMSS)
1225 W. Dayton Street
Madison, WI  53706  USA
ph: +1 608 262 2759

• References:
  • [visad] GOES AREA goerefencing
    • From: Luis Martín Pomares